The present invention relates to a controller apparatus for driving an electric vehicle, and more particularly to a controller apparatus capable of preventing the vehicle from running way due to trouble of the controller.
The controller apparatus for an electric vehicle as shown in FIG. 13 has been proposed.
In FIG. 13, reference numeral 1 define a battery as a power supply, which is charged by a power generator (not shown) and supplying DC power to electric load; 2, an invertor main circuit which is a power converter section for converting the DC power supplied from the battery 1 into AC power; 3, an induction motor for driving an electric vehicle in response to the output from the invertor main circuit 2; 4, a contactor which is a switch arranged on a power supply path from the battery 1 to the invertor main circuit 2; 5, a pulse generator for detecting the rotary speed of the induction motor 3; 6, an AC current sensor for detecting the current flowing through the induction motor 3; and 7, an accelerator opening sensor for detecting the opening of an accelerator (not shown), which may be e.g. a potentiometer generating the voltage corresponding to an accelerator opening. The accelerator opening, which corresponds to the pressing amount of an acceleration pedal (not shown) being pressed by a driver, indicates the torque required by the driver. The controller apparatus further includes an opening/torque conversion memory 8 for generating the signal (hereinafter referred to as a torque command value) corresponding to a desired torque on the basis of the detected output from the accelerator opening sensor 7.
The opening/torque conversion memory 8 has an output characteristic as shown in FIG. 11. It outputs the torque command which causes the induction motor 3 to provide the torque of 15.8 Kgf.multidot.m when the output from the accelerator opening sensor 7 is 3.86 V assuming that the rotary speed of the induction motor 3 is 2100 rpm. Incidentally, in FIG. 11, the accelerator opening being of zero corresponds to when regenerative braking is carried out (electric braking state) or the vehicle is at rest. At the time of regenerative braking, the opening/torque conversion memory 8 outputs the torque command value of 0 to -15.8 Kgf.multidot.m corresponding to the rotary speed of the induction motor 3. Furthermore, in FIG. 13, reference numeral 9 defines a function generator for controlling the invertor main circuit 2 by vector-operating the value and frequency of a voltage applied to the induction motor 3 on the basis of the output signals from the pulse generator 5 and the AC current sensor 6 and various input signals (not shown). The function generator 9 and the opening/torque conversion memory 8 constitute a control section and can be organized by a microcomputer.
The thus configured controller apparatus for an electric vehicle controls transistors 2a to 2f in the invertor main circuit 2 on the basis of the torque command value and output from the function generator 9 to drive the induction motor 3, thereby providing a driving force characteristic as shown in FIG. 10. FIG. 10 shows the driving force characteristic required by general electric vehicles. The transistors 2a to 2f serve to change the value and frequency of the voltage applied to the induction motor 3 by PWM (pulse width modulation). The technique for controlling the above induction motor is well known so that its operation is not explained in detail here.
The above conventional controller apparatus for an electric vehicle has the following defects. For example, when the opening/torque conversion memory 8 or the function generator suffers any failure, i.e. in the event of failure of the microcomputer and several kinds of components such as an A/D converter, the torque command value larger than the opening of an accelerator, i.e. the torque required by a driver may be output so that excess power may be supplied to the induction motor 2. As a result, the electric vehicle may runaway.